<!DOCTYPE html>
<html>
  <head>
    <style>
.row > div {
  height: 64px;
  float: left;
}

.row { clear: both; }
.row > :nth-child(1) { width: 32px; }
.row > :nth-child(2) { width: 64px; }
.red { background-color: red; }
.green { background-color: green; }
    </style>
  </head>
  <body>
    <div class="row">
      <div class="red"></div>
      <div class="green"></div>
    </div>
    <div class="row">
      <div class="green"></div>
      <div class="red"></div>
    </div>
  </body>
</html>
